of wilmington



Patented June.30, 1931 UNITED STATES PATENT OFFICE ARNOLD M. COLLINS, OF WILMINGTON, LELAWARE, ASSIGNOR TO E. I. DU PONT NEMOURS & COMPANY, OF WILMINGTON, DELAWARE, A CORPORATION 'OF DELA- WARE N Drawing.

This invention relates to the art of drying oils and, more particularly, to synthetic drying oils and the process of making them.

Although drying oils, such as linseed and China wood oil, and varnishes made from them, yield films of excellent flexibility, ad-

. hesion, durability, and resistance to the ac tion of water, these oils and'varnishes dry and harden too slowly to be advantageously used for many purposes Where speed is an important consideration. Accordingly, they are being'replaced, to some extent, by nitrocellulose lacquers WhlCll,lIOW6V8I', have the disadvantage of being more costly. Furthermore, since the drying oilsnow known are all derived from vegetable or animal products, many of which are brought from foreign countries, their cost and availability are subject to considerable variation.

I have found that highly unsaturated hydrocarbons, such as divinyl acetylene, may

be polymerized to form liquid, non-volatile products which have the general'characteristics of drying oil but possess numerous advantagesthereover, and may be used to form coating compositions which are superior to those heretofore in use.

It istherefore an object of my invention I to provide synthetic drying oils.

I which will be apparent as the description proceeds, I have set forth my invention in the following specification and have included the following examples by way of illustration and not as a limitation.

Ewample'l 1000 grams of pure divinyl acetylene is boiled at atmospheric pressure and in the presence of air for 4 hours in a' vessel provided with a condenser for the return of the condensed vapors-to the reaction. The temf the'boiling' liquid is between 85 At the end of 4 hours the un- SYNTHETIC DRYING OIL AND PROCESS OF MAKING I'I Application filed August 7, 1929. Serial No'. 384,238;

changed divinyl acetylene is distilled off under reduced pressure: There remains, in

12 to 18% yield, a viscous non-volatile residue having the general properties of a bodied drying oil and consisting of the polymerized divinyl acetylene. This may be thinned to a.

viscosity suitable for application by brushing, spraying, etc. by the addition of solvent naphtha.

Example 2 1000 grams of pure divinyl acetylene is boiled as in Example 1, except that 20 grams of cobalt linoleate containing 10% of cobalt is added and the heating lasts only 2 hours. The unchanged divinyl acetylene is removed as above and the viscous residue, amounting to 12% of the original material, is thinned as in Example 1. Ewample 3 sure in a closed vessel at 100 C. for 3 hours or until its refractive index (measured at C. with the D line of the spectrum) is approximately 1.578. A practically nonvolatile yellow liquid results which'is thin enough and has very desirable drying properties for application as a lacquer or varnish by the usual methods The yield is about 100%.

, Example 5 40 grams of dibutylamine,'1000 grams of crude divinyl acetylene containing about 40% of a tetramer of acetylene,'and 1000 grams of xylene are boiled at atmospheric pressure under a reflux condenser for hours, the air in the apparatus being replaced by nitrogen. In this Way practically complete conversion relatively low viscosity and having good drying properties, and usually requires no thinning before use;

Example 6 v 1000 grams of crude divinyl acetylene contaiiiing 25% of a tetramer of acetylene is boiled at 75-80? 0., at atmospheric pressure, under a'reflux condenser and in an atmosphere of nitrogen for 5 hours. The resulting solution of polymers in unchanged. hydrocarbons is used as a drying oil after distillin off any unchanged portion of the origina- 50% based on the original acetylene mixture and this yield is independent of the optional treatment with xylene.

- Est-ample 7 78 grams of divinyl acetylene. hydrogenated in the usual manner with 44.8 liters of hydrogen in the presence of a latmum catalyst. The resulting mixture 0 unsaturated hydrocarbons ispolymerized by heating in a sealed tube for 3 hours at 180 C.

After the removal of the unchanged hydrocarbons by vacuum distillation aviscous oil,

similar to that obtained in Example 1, is"

obtained.

The divinyl acetylene referred to above is preferably prepared by mixing 945 parts by weight of ammonium chloride, 1000 parts by l weight of water, 2850 parts by weight of cuprous chloride, and 100 parts by weight of copper powder, and agitating this mixture thoroughly while passing into it acetylene gas. When the reaction slows up, as shownbya decrease in the rate of absorption of acetylene, the operation is discontinued, and the highly unsaturated hydrocarbon product formed is obtained by distillation, which is stopped when the condensed hydrocarbon is mixed with much water. The water is separated and returned to' the reaction I mass which, after cooling, is ready for the ,absor tion of more acetylene. It is preferab e,

V although not essential, to keep thereactiontemperature at a proximately 25 C. by

suitable cooling'of e reaction mass.

In the preparation of divinyl acetylene by the method indicated above the resulting product contains .a tetramerof acetylene in amounts of from 25-40 the higher amounts of the tetramerbeing obtained when part of of air or by the presence of an inert gas,

the divinyl acetylene is removed by distillation. I have found that the presence of the tetramer, which is believed to be butadienyl vinyl acetylene, is desirable inasmuch as it increases the yield of synthetic drying oil.

' Although the above exainples are limit-ed to the use of divinyl acetylene and a tetramer of acetylene, and reduction products of divinyl acetylene,other unsaturated hydrocarbons, such as other polymerizable polymers ofacetylene and other partial reduction products containing at least two and preferably threeunsaturated bonds, or the homologs or isomers of these compounds, may be used. Thus, I may employ such compounds as butadiene and its homologs dimethyl buta die'ne, isoprene, piperylene, and the like as Well as compounds of the type of dipropargyl,

which contain triple bonds but no double bonds. Furthermore, it is not necessary to use pure compounds in making the synthetic drying oils. In fact, as indicated above, it is sometimes advanta eous to polymerize mixtures of unsatura d hydrocarbons. Thus,

as indicated above, I may first partially hydrogena-te divinyl acetylene to a mixture containing such compounds as divinyl ethyl'ene, vinyl ethyl ethylene, and vinyl ethyl acetylene, and then v polymerize this mixture. The hydrocarbons discussed in this para graph will be referred to generally as. polymerizable aliphatic hydrocarbons containing at least two and preferably three unsaturated bonds. 1

These unsaturated hydrocarbons may be polymerized at any temperature below that at which decomposition occurs, but, in gen- 1 eral, I have found a temperature between 80 and C. to be the most suitable for divinyl acetylene and a tetramer of acetylene. For more nearly saturated compounds higher temperatures are preferable. Heatmg may be continued to any point short of the formation of an insoluble gel, at which time any remaining unchanged hydrocarbon is distilled off. The synthetic drying oils obtained are more or less viscousliquids, nonvolatile at ordinary temperatures and .con-

sist of compounds containing at least 12 car- 5 bon atom's and'havinga molecular weight of at least 156. The rate-of polymerization .va-

'ries with the type ofnunsaturated.hydrocarbon used, and may be increased by increasing the temperature, or by the'preisence of oxygen -with or without those substances known tothe varnish art'as driers. It may be decreased,on the other hand by decreasing the temperature, by dilution with solvents,

and by the addition of antioxidants in rela-v tively small amounts. The yield-of poly m'erized material obtainable before gelation occurs is increased by the use of solvents, such as aromatic hydrocarbons, peptizingagentg such as aliphatic amines, and by the exclusion i such is nitrogen or carbon dioxide. In some cases it is more advantageous to discontinue the polymerization .when only a portion of the startin g material has been converted. I The removal of the unchanged material renders the heat polymerized'polymerizable polymer more stable against skinning and solidifying in the container. .Any un lymerized material removed may be use for the manufacture of more synthetic dryingoil. The average molecular weight, viscosity, and solubility of'the synthetic drying oils may be controlled by varying the temperature and time of heating. Thus, longer heating yieldsproducts of higher molecular weight, greater viscosity, and-decreased solubility in such solvents as aliphatic hydrocarbons. Sufliciently long heating will finally cause the gelation or solidification of the entire mass. The gels are insoluble in all solvents and hence not usable as coating compositions. In preparing synthetic drying oils heating must therefore be discontinued before the material reaches the insoluble stage. I have found, however, that non-volatileliquid materials in any stage of polymerization between that represented by an average molecular weight of 156 and that just short of the formation of a gel are suitable for use as synthetic drying 011s.

In order that the synthetic drying oils may be used to formv the most desirable coating compositions, I may control their flexibility, viscosity, and drying characteristics either during or after polymerization. Thus the flexibility may be increased by the addition.

of rubber softeners. The viscosity may be increased by the addition of synthetic resins,

like meta styrene, or other viscous, film-formmg material which is compatible with the synthetic drying oils, or it may be decreased by dilution with solvents such as xylene, acetone, or butyl acetate in theusual manner or by the addition of small amounts of am1nes.

These synthetic drying oils dry and harden in thin films, without substantial loss of weight (not over 1%), on exposure to air at ordinary or elevated temperatures. The rate at which the films dry may be increased by the addition of driers, such as soluble com-'- pounds of lead, cobalt, and manganese. Because of the'rapid absorption of oxygen by these synthetic drying oils, it has'been found advantageous in some cases to add a small amount of an antioxydant, e, g. eugenol, in order to reduce the tendency to skin and solidify in the container. The amount of anti Xidant is controlled so that it does not alter he thin film dryin rate to an objectionable degree for practical purposes.

It will therefore be apparent that I have developed a new class of non-volatile, soluble drying oils, which may be made synthetically from cheap and readily available substances and a process of producing them. Films of these drying oils dry more rapidly and harder than films containing natural drying oils, and are completely resistant to the action of water, organic solvents, strong acids and alkalies. No claims are made herein to polymerizmerization as this subject matter is disclosed and claimed in a co-pending application of Calc'ott' and Downing, Senal No. 288,528 filed June 2c, 1928. 7

Furthermore, no claims are made herein to coating compositions containing synthetic drying oils because this subject matter is disclosed and claimed my co-pending application filed of even date herewith, Serial No. 384,239.

By the term non-volatile,.as used herein, I mean that when heated to 100 C. at a pressure corresponding to 35 mm. of mercury nothing is distilled off.

As many apparently Widely different embodiments of this invention may be made without departing from the spirit and scope' thereof, it is to be understood that I do not limit myself. to the specific embodiments thereofexcept as defined in the appended patent claims.

I claim i 1.. The process of polymerizing divinyl acetylene which comprises effecting the polymerization in the presence of an added solvent.

2. As a new product, a body consisting of an open chain acetone soluble liquid which isnon-volatile at 100 C. and is a polymerization'product of a member of the group which consists of polymerizable aliphatic hydrocarbons containing at least 3 unsaturated bonds.

3. As a new product, a body consistin of an open chain liquid polymerization pro not of a polymer of acetylene which product is non-volatile at 100 C.

4. A synthetic drying oil consisting of a liquid open chain polymer of a material containing divinyl acetylene which polymer is non-volatile at 100 C.

5. A liquid open chain polymerization product of an open chain polymerizable polymer of acetylene, which product is non-volatile at 100 C. and is obtained by exposing said polymer of acetylene to air to effect polymerization and subsequently removing the re-,

maining constituents which are volatile at 100 C. by distillation in vacuo. 6. An open chain polymerization product of an open chain liquid polymerizable polymer of acetylene, which product is non-volatile at100 C. and is obtained'by exposing said polymer of acetylene to air to produce a viscous liquid by polymerization and subsequently removing the remaining constituents which are volatile at 100 C. by distillation.

7. A liquid open chain polymerization product of an open chain liquid polymerizable polymer of acetylene,. which product is non-volatile at 100 C. and is obtained by exposing said polymer of acetylene to air and heat until a viscous liquid results, and subsequently removing the remaining polymers which are volatile at 100 C. by distillation in vacuo.

8. A liquid open chain polymer'izable polyi mer of a volatile liquid polymerizable acetylene polymer, which product is non-volatile at 100 C. and is obtained by heating said acetylene polymer at temperatures below 100 C. and without exclusion of air for from two to three hours, and subsequently removquently removing therefrom by distillation in vacuo any remaining polymers which are volatile at 100?v C.

10. In theprocess of polymerizing an open chain hydrocarbon which contains at least 3 unsaturated bonds thestep of heating the hydrocarbon in the presence of an added solvent for the polymer and discontinuing the heating prior to the formation of a gel.

11. The process of polymerizing an open which comprises heating a mixture contail ing divinyl acetylene and a tetramer c acetylene at 7580 C. for 5 hours atatmo: pheric pressure, and removing any ur changed divinyl. acetylene and tetramer c acetylene.

16. The process of claim 15, in which th heating is carried out in an atmosphere c nitrogen. i

17. The process which comprises heatin an aliphatic hydrocarbon comprising an ope chain polymerizable polymer of acetyler containing at least two unsaturated bonds t efiect polymerization, discontinuing tl". heating before theformation of a gel, an while the material is still readily soluble i acetone, and removing any unchanged hydn carbon to obtain an oil having the propertie of a drying oil and non-volatile at 100 C.

18. The process of claim 17 in which th material subjected to polymerization include divinyl acetylene, the temperature does nc exceed-100 O. and the heating is continue to produce anon-volatile liquid containing a least. 12 carbon atoms a'ndhaving a molecula weight of at least 156.

In testimony whereof, I aflix my .signatun ARNOLD M. COLLINS.

chain liquid polymer of acetylene which comprises effecting the polymerization by heating in the presence of an added solvent.

12. The process which comprises heating an open chain polymerizable acetylene polymer to effect a degree of polymerization corresponding to that obtainable by heating said polymer to a temperature of at least 75 C. for at least 2 hours at atmospheric pressure, and removing any unchanged hydrocarbon to obtain a non-volatile oil having the properties of a dryingoil, and distilling at temperatures above 100 C.

13. The process of claim'12, in which the material subjected to polymerization comprises divinyl acetylene, and is heated to a temperature not substantially in excess ofp 14. The process of claim 12, in which the material subjected to polymerization com- ;,prises divinyl acetylene and a tetramer of acetylene, and is heated to a temperature g 

